1. Field of the Invention
This invention relates to the formation of plastisol films and more particularly to compositions useful in the formation of such plastisol films. More specifically, the invention relates to a composition for application to a carrier cloth upon which plastisol films are formed for the purpose of delustering the surface of the formed plastisol film and for effecting ready release of the formed plastisol film from the coated carrier.
2. Description of the Prior Art
Plastisol resin compositions are well known in the art and generally comprise dispersions of thermoplastic resins in the form of fine particles, the dispersion medium being a plasticizer for the resin. Such dispersions have appreciable fluidity in normal temperatures but are generally converted by heat into a flexible, tough thermoplastic member by the process of fusion wherein the resin becomes plasticized and solvated by the plasticizer. Such plastisol resin materials have been useful in the formation of numerous different products such as upholstery, fabric coverings, coverings for various objects and for camouflage. Such plastisol resin coatings are frequently formed by laying down a layer of the liquid plasticizer on the fabric to be coated and then subjecting the coated fabric to an elevated temperature to cure and plasticize the resin to form the hard plastisol layer. Examples of such formation processes and the uses for such plastisols are disclosed in U.S. Pat. No. 2,566,982 and U.S. Pat. No. 3,076,234.
As previously mentioned, plastisol films are also useful in the construction of camouflage materials. In the formation of such plastisol films, the liquid plastisol is laid down on a continuous carrier cloth material, cured, and then separated from the carrier material. This separated plastisol film is then combined with another layer of plastisol film and a backing substrate material to form camouflage materials. Thus, in the formation of camouflage, the plastisol film does not remain secured to the carrier cloth upon which it is formed. One example of such a formation process of plastisol film for camouflage is illustrated in U.S. patent application Ser. No. 920,958, filed June 30, 1978, by Kenneth Morton, and assigned to the assignee of the present application.
There are several problems particular to the formation of plastisol films for camouflage purposes where the plastisol film must be separated from the carrier cloth. One such problem is that under normal circumstances, the cured plastisol film has a highly lusterous finish. However, camouflage requirements necessitate that the surface of the camouflage material to be viewed must be dull and matte. Thus, when the plastisol film is separated from the carrier cloth, the surface of the plastisol film which abutted the carrier cloth must in some manner be formed with a dull, matte finish. In other words, the surface must be delustered (the normal luster of the plastisol must be removed).
A second problem with the above is that the plastisol film must be readily and easily separated from the carrier cloth after its formation so that it does not adhere to the cloth. Otherwise, pieces of the plastisol film may be removed from the film and retained on the carrier, and the plastisol film may even tend to tear during separation.
Heretofore, the above-described problems were overcome only with considerable expense and difficulty. For example, to achieve proper delustering of the plastisol film surface and to insure easy separation of the plastisol film from the carrier cloth, the carrier cloth was in one instance coated on both sides with two layers of a non-drying coconut oil alkyd containing colloidal silica. In addition, the side of the cloth to be used for formation of the plastisol film was given a top coat of a silicone resin. After the formation of each coating on one surface of the carrier cloth, this coating was then subjected to heat to cure the resin material. Thus, to properly treat the carrier cloth, five separate coating and curing cycles were required. The silicone top coat acted as a release agent for the fused vinyl plastisol film to permit ready release of the film from the carrier cloth after the formation of the film.
The difficulties with the previously described solutions to the aforementioned problems are several. First, considerable time and expense is required to separately apply and cure five different coatings on a long continuous roll of carrier cloth. Second, in order to insure that each coating will adhere to the prior applied coating, the chemical composition and coating quantity parameters have to be closely controlled. Otherwise, a subsequent coating would not completely adhere to a prior applied coating on the carrier cloth. Third, in order to obtain the proper delustering of the plastisol film bottom surface, careful comparison tests have to be run for each color of plastisol film to be formed on a particular cloth having the five coated layers thereon. Such tests are time consuming and expensive. However, if they are not performed, proper delustering of the plastisol film can not be insured. Therefore, each time the color of the plastisol film to be formed was to be changed, such comparison tests were required. Fourth, since the rolls of carrier cloth are quite long and expensive, it is highly desirable to be able to reuse a roll of carrier cloth upward to one hundred times or more. Thus, the coatings applied to the cloth to achieve proper delustering and release of the plastisol film must function properly throughout the life of the carrier cloth. In order to achieve such repeated usage, considerable time and effort must be expended when applying the various coatings to the carrier cloth to insure proper binding between the coatings as well as proper amounts. One example of such a problem is that if too much of the alkyd coating to the first surface of the cloth is applied so that the resin penetrates entirely through the cloth, the alkyd layer applied to the opposite side of the cloth will not properly adhere thereto. Furthermore, even if considerable time and quality control are utilized when applying the coatings to the carrier cloth, frequently the carrier cloths will not properly release the plastisol film after only a relatively few uses. Therefore, such a cloth would have to either be prematurely discarded or recoated with the silicone resin overcoat.
The present invention readily overcomes the problem of insuring proper delustering of the plastisol film surface and insuring ready release of the plastisol film from the carrier cloth while permitting the carrier cloth to be reused in excess of one hundred times without further treatment of the cloth. The present invention overcomes these problems while simultaneously obviates the previously described deficiencies and difficulties of the prior carrier cloth coating technique.